Epidemiol. Infect., Page 1 of 7. f Cambridge University Press 2010 doi:10.1017/S0950268810000695 Nipah virus outbreak with person-to-person transmission in a district of Bangladesh, 2007 N. HOMAIRA 1,2*, M. RAHMAN 1,M.J.HOSSAIN2, J.H. EPSTEIN3,4, R. SULTANA2,M.S.U.KHAN2,G.PODDER2, K. NAHAR2,B.AHMED1, E. S. GURLEY 2,P.DASZAK4,W.I.LIPKIN5, P.E. ROLLIN6,J.A.COMER6, 6,7 2,6 T. G. KSIAZEK AND S. P. LUBY 1 Institute of Epidemiology, Disease Control and Research (IEDCR) Dhaka, Bangladesh 2 International Centre for Diarrhoeal Disease Research, Bangladesh (ICDDR,B), Dhaka, Bangladesh 3 The Consortium for Conservation Medicine (CCM), New York, USA 4 Wildlife Trust, New York, NY USA 5 Center for Infection and Immunity, Columbia University, New York, USA 6 Special Pathogens Branch, Division of Viral and Rickettsial Disease, National Centre for Infectious Disease, Centers for Disease Control and Prevention (CDC), Atlanta, GA, USA 7 Galveston National Laboratory, Department of Pathology, Galveston TX, USA (Accepted 9 March 2010) SUMMARY In February 2007 an outbreak of Nipah virus (NiV) encephalitis in Thakurgaon District of northwest Bangladesh affected seven people, three of whom died. All subsequent cases developed illness 7–14 days after close physical contact with the index case while he was ill. Cases were more likely than controls to have been in the same room (100% vs.9.5%, OR undefined, P<0.001) and to have touched him (83% vs. 0%, OR undefined, P<0.001). Although the source of infection for the index case was not identified, 50% of Pteropus bats sampled from near the outbreak area 1 month after the outbreak had antibodies to NiV confirming the presence of the virus in the area. The outbreak was spread by person-to-person transmission. Risk of NiV infection in family caregivers highlights the need for infection control practices to limit transmission of potentially infectious body secretions. Key words: Bangladesh, Nipah virus, person-to-person transmission. INTRODUCTION Antibodies reactive to NiV antigen have been de- tected in pteropid bats in both India and Bangladesh In Bangladesh, Nipah virus (NiV) was first identified [1, 5]. as the cause of an outbreak of encephalitis in 2001 Person-to-person transmission of NiV infection, in Meherpur District [1, 2]. Four additional out- following human infection directly from the environ- breaks were identified between 2001 and 2005 [1–4]. ment, was noted in previous outbreaks in the Indian subcontinent. In a NiV outbreak in Siliguri, India * Author for correspondence: Dr N. Homaira, Programme on in 2001, 45 patients (75%) had a history of hospital Infectious Disease and Vaccine Sciences, Health System and exposure to other patients with NiV infection [6]. Infectious Disease Division, ICDDR,B, 68, Shahid Tajuddin In Faridpur District, Bangladesh in 2004 NiV case- Ahmed Sharani, Mohakhali, Dhaka-1212, Bangladesh. (Email: [email protected]) patients in Faridpur were seven times more likely than 2 N. Homaira and others non-patients to have had close contact with one of the immunosorbent assay (ELISA) that detects IgM NiV patients [odds ratio (OR) 6.7, 95% confidence antibodies specific for NiV antigens [7]. interval (CI) 2.9–16.8, P<0.001] [2]. We defined a confirmed case of NiV infection as a On 9 February 2007, a physician at Rangpur Medi- suspected case-patient with detectable IgM to NiV. cal College Hospital, one of 10 hospitals involved in The team defined a probable NiV case-patient as a active NiV encephalitis surveillance in Bangladesh, patient with fever and altered mental status who lived reported a cluster of fatal encephalitis involving a in the same village as a confirmed case-patient during husband and a wife residing in the Haripur Upazila the outbreak period, but from whom serum was not (subdistrict) of Thakurgaon District. Both patients available because the patient died before a specimen had similar symptoms and died within an interval could be collected. of 2 weeks. A collaborative team including the Insti- tute of Epidemiology Disease Control and Research Qualitative study (IEDCR) and the International Centre for Diarrhoeal Disease Research, Bangladesh (ICDDR,B), began an A team of experienced anthropologists conducted investigation on 10 February 2007. The objectives in-depth interviews and informal discussions with of the investigation were to identify the cause of the available confirmed and probable case-patients, their outbreak and the risk factors for developing illness. family members and friends, and other residents in these communities with the goals of exploring poten- tial exposures to NiV and identifying appropriate METHODS proxy respondents for deceased cases or cases that were too sick to interview. The anthropologists also Case definition and identification collected information about symptoms of the disease, We defined suspected case-patients as persons having caregiving practices and health facility utilization by fever with altered mental status or new onset of persons affected by the outbreak. seizures (severe illness), or persons having fever with headache or cough (mild illness), residing in the out- Case-control study break area with an onset of illness between 15 January and 28 February 2007. The team visited the outbreak We conducted a case-control study to investigate village and asked the community health workers and exposures associated with NiV infection, including community residents if they were aware of any patient person-to-person transmission. Probable and con- who was suffering from fever with seizure or altered firmed case-patients were enrolled as cases. We selec- mental status, or who had died from these symptoms ted three controls for each case-patient. Controls in their neighbourhood. We also asked them about were selected starting from the fourth closest house to case-patients suffering from fever with headache and/ the case-patient where no members were ill during or cough. The team then visited the local hospital the outbreak. The household resident closest in age in order to identify suspected case-patients. Team to the case-patient was eligible to participate as a members also investigated all the deaths in the out- control. Participation was voluntary. If the selected break village between January and February. We ob- household resident declined to participate, a resident tained a history of illness and general information from the next closest house was asked to participate. about exposures for each suspected case-patient. We The qualitative team selected proxy respondents asked the local health authority of the affected sub- for each case-patient who had died or was unable to district to report to the IEDCR if they identified respond. The proxy respondents included family any further suspected case-patient having fever and members and friends of the case-patients who were altered mental status or seizures who sought treat- most knowledgeable about their activities and prob- ment in the local subdistrict health complex during able risk exposures in the preceding 1 month before February. illness. Multiple proxy respondents were common. The team collected blood samples from living sus- The investigation team used a standardized question- pected case-patients, which were centrifuged in the naire to collect information on demographics, symp- field and transported on wet ice to IEDCR, where toms of illness, and possible risk factors associated they were stored at x70x. Samples were tested with with NiV transmission including history of con- an immunoglobulin M (IgM) capture enzyme-linked sumption of date palm juice prior to illness, exposure Person-to-person transmission of NiV 3 to animals and exposure to ill patients, including outbreak investigation. Bat capture and sample col- touching, staying in the same room, feeding, sharing a lection was conducted under a protocol approved by bed or cleaning body secretions of a NiV patient. the Institutional Animal Care and Use Committee. Bat survey RESULTS A team of veterinarians from ICDDR,B with assist- Descriptive epidemiology ance from the Consortium for Conservation Medicine located two bat roosts which were 1 km and 15 km Eleven serum samples were collected from 13 sus- distant from the outbreak village. Bats were captured pected case-patients. Five suspected case-patients using mist nets and were anaesthetized during sample had IgM antibodies against NiV by capture ELISA collection and released at the point of capture after and were thus confirmed cases. Two suspected case- sampling from 24 February to 9 March 2007. All patients had fever and altered mental status, but died the captured bats from which blood samples were before samples could be collected and were categor- collected were P. giganteus. ized as probable cases. These two probable cases were All bat blood samples were kept on ice until the the index case and his wife. The remainder of the end of each day when serum was separated and stored analysis was performed on these seven confirmed or in liquid nitrogen. At the end of each day, blood probable case-patients. Five of these case-patients samples were transferred to liquid nitrogen and (three confirmed and two probable) had fever with transported to ICDDR,B where they were stored at altered mental status and three (60%) of them died. x70 xC and then shipped on dry ice to the Australian A total of five case-patients, including the two prob- Animal Health Laboratory for laboratory diagnosis. able cases, were hospitalized. The mean age of case- All the blood samples were assayed for antibodies patients was 24 years (range 19–30 years) and five against NiV using a serum neutralization test. (71%) were male. The median duration from onset of fever to death was 5.6 days (range 5–7) (Table 1). Fever (100%), altered consciousness (71%) along Statistics with vomiting (71%) and cough (71%) were the most We analysed socio-demographic and clinical profiles common symptoms (Table 1).